Conductivity-based model for the simulation of homocharges and heterocharges in XLPE high-voltage direct current cable insulation

The dynamic space charge distribution within cross-linked polyethylene (XLPE) cable insulations is simulated in this study. To simulate charge dynamics inside the insulation, different models have been developed. Conductivity-based models describe electronic and ionic charges. Such models are structurally simpler than bipolar charge transport models because of their macroscopic description. So far, the macroscopic description is insufficient, as it does not depict the accumulation of homocharges and heterocharges near the electrodes and the transport of charge packets. In this study, a conductivity-based model is developed to simulate the transport of charges and the formation of homocharges and heterocharges. The conductivity model depends on the electric field and on the temperature. This model is extended by two Gaussian curves, moving from the electrodes to the counter electrodes, which features an increased conductivity in comparison to bulk conductivity. The bulk conductivity is obtained from measurements in the literature. The permittivity is modelled to be non-constant in the vicinity of the electrodes due to e.g. interdiffusion between the bulk insulation and the semiconducting layer. A comparison between the simulation results and the reference measurements confirms the applicability of the presented approach for the description of the dynamic charge distribution in XLPE cable insulation.